High voltage (e.g., 5 to 35 kV) electrical power cables, which generally comprise a stranded conductor surrounded by a semi-conducting conductor shield, a polymeric insulation jacket, and an insulation shield, tend to deteriorate and lose dielectric integrity after being in service for a decade or more due to exposure to high electric fields and the effects of ambient moisture. The integrity, or dielectric strength, of the cable can be at least partially restored by injecting a dielectric enhancement fluid into the interstitial void volume associated with the stranded conductor, as is well known in the art (e.g., U.S. Pat. Nos. 4,766,011 and 5,372,841). Various specialized connectors have been designed to facilitate the injection of such a fluid into the cable's interior and some of these devices allow the injection process to be carried out while the cable is still energized. However, a problem associated with such a live injection process soon became apparent. In brief, when an injection component, such as that described in U.S. Pat. No. 4,946,393, is used to deliver the dielectric enhancement fluid, the energized conductor is exposed between the time an injection plug (cap) is withdrawn from the injection port after the fluid has been introduced and the time an insulating permanent plug is inserted in its stead to seal the injection port. During this interval it is possible that the high voltage may ionize the air, water, injection fluids, or other materials in the injection port and a flashover may occur between the conductor or the conductive insert of the component and a ground plane. Such an arc flash can damage the equipment, the component, the transformer or other equipment in the immediate area and presents a thermal and electrical danger for the operator as these plugs are being swapped. Although flashover is possible at all power cable voltages, the risk increases with increasing voltage and the risk is greatest with 35 kV systems. In fact, the risk is so great at 35 kV that such “live plug swapping” is not practiced with currently utilized technology, and the cable is de-energized before the swap. While de-energizing the cable eliminates the potential for electrical flashover, there is a cost and customer service penalty that must be borne by the circuit owner for the additional time, expense and inconvenience of this approach, as well as stress on the cable.
The above mentioned flashover problem is described in greater detail in U.S. Pat. Nos. 6,517,366 and 6,929,492, and a solution thereto is disclosed such that the whole injection process can be carried out without de-energizing the cable. These patents are directed towards a method and apparatus for creating a barrier after the injection of remediation fluid to block the conductive pathway between the conductive portion of an energized cable and the ground plane. Basically, this barrier comprises some sort of a mechanical valve that can be actuated to isolate the conductor from the exterior of the component, a breakaway tip which lodges in the injection port, or a high viscosity dielectric fluid which is introduced into the injection port of a component after injection of the dielectric enhancement fluid has been completed to temporarily block the port while the permanent plug is swapped for the injection plug. Complex mechanical valves add cost to the process and, if they reside within the outer boundary of the connector's conductive insert, they do not foreclose the possibility of a flashover even if they operate properly. Injecting a second fluid into the cap or plug adds another layer of complexity and cost. There is thus a need for a simpler and more cost-effective approach to provide safe operation during the injection of an energized cable.